1. Field of the Invention
This invention relates in general to pulse slimming, circuits, and in particular to slimming the pulses which are generated when data is read from the storage disks of a hard disk drive.
2. Description of the Related Art
In the hard disk drive digital storage art, an information bearing signal in the form of write current pulses passes through a write head and induces a corresponding magnetic pattern on the hard disk moving under the head. The hard disk maintains its magnetization which constitutes stored digital information. Read back is the process in reverse: the magnetization on the disk (platter) induces varying electric currents in a read head.
As computer programs and applications demand ever increasing amounts of memory, the density of data to be stored on each disk or platter within a hard disk drive and the rate at which that information can be stored and read is ever increasing. As storage density and data rates increase, interference between pulses and other related problems grow worse.
Some past patents have modified the spectral contour of the signal after it has been read back from the hard disk to compensate for changes due to temperature variations in the environment in which the hard disk drive is operating. U.S. Pat. No. 4,479,152 to Chi issued Oct. 23, 1984 shows such a system. The Chi patent subtracts a single delayed and amplitude modified signal from the original signal in order to compensate for changes of temperature, pressure or other conditions. The amount of delay and amplitude modification can be varied among a fixed set of choices according to the physical conditions in which the hard disk drive is operating.
However, such simple systems provide quite limited improvements in performance. What is needed is a more sophisticated system for more effectively slimming the data pulses so that greater storage densities and data rates can be utilized.